diff --git a/packages/mermaid/src/diagrams/flowchart/flowDb.ts b/packages/mermaid/src/diagrams/flowchart/flowDb.ts
index 54152c7ac..8a596209e 100644
--- a/packages/mermaid/src/diagrams/flowchart/flowDb.ts
+++ b/packages/mermaid/src/diagrams/flowchart/flowDb.ts
@@ -270,7 +270,7 @@ export const setClass = function (ids: string, className: string) {
 };
 
 const setTooltip = function (ids: string, tooltip: string) {
-  if (!tooltip) {
+  if (tooltip === undefined) {
     return;
   }
   tooltip = sanitizeText(tooltip);